Heads for exchanging information in the form of distributed magnetic patterns depend for their utility upon the handling of magnetic flux within a magnetic circuit. That is, such heads sense or transmit information by handling magnetic flux within their magnetic circuits. Magnetic writing is accomplished by injecting a magnetic flux into the head magnetic circuit and thence to the magnetically receptive and retentive medium. This is normally a function provided by energizing a coil coupled to the magnetic flux path.
Where detection of data from the medium is via a coil around the flux path, detected signals are proportioned to the flux change rather than the steady state flux magnitude. Conversely, where a magnetoresistive device or a SQUID is employed, the magnitude of the flux linking the device is sensed directly. SQUID is a contemporary acronym for Superconducting Quantum Interference Device. There are a variety of prior art approaches to concentrating and controlling the magnetic field in magnetic read/write heads for recording and reading with respect to magnetic media.
The magnetic flux circuit for conventional such heads are sometimes established by fabricating the head in a ring configuration ending in a gap or by bonding C-bar and I-bar units with a defined gap therebetween. Some prior art such heads included metal in the gap for the purpose of diverting the magnetic flux outwardly from the gap towards the magnetic media.
Sometimes the gap flux concentration enhancements take the form of sandwiches of conducting and insulating material to establish eddy currents at the gap to create magnetic forces diverting the flux from the head circuit. Examples of this are shown in U.S. Pat. Nos. 3,072,750 by Barry, 3,246,384 by Vice, 3,508,014 by Mersing and 4,646,184 by Goto et al. Japanese application Ser. No. 60-151315 by Ogawa which it is understood was published on Aug. 14, 1984 employs a recording head with the magnetic flux path interrupted at the gap by a superconductor material. It is known that a material in its superconductive state may block passage of magnetic flux therethrough with appropriate thickness, quality and H-field level (the Meissner effect). It may also guide magnetic flux through vortex regions and bend flux lines towards the material surface. Accordingly, the superconductive plug in the Ogawa head gap should cause maximum magnetic flux density outwardly from the gap and in the direction of the media.
Typically data is recorded on a magnetic media by magnetizing a magnetic layer of the media in a longitudinal direction parallel to the direction of relative movement between the head or transducer and the medium. It is known that improved data density on the media is possible by the use of perpendicular data cell recording. For perpendicular recording, data cells are established by magnetizing the magnetic recording layer in a direction perpendicular to the media surface.
Further data density improvements are obtained by applying thin film construction techniques to the assembly of magnetic read/write heads. An arrangement for perpendicular recording with laminated thin film layers including both a read/write element and a tunnel erase pole is shown in U.S. Pat. No. 4,541,026 by Bonin and Dugas. Longitudinal recording heads fabricated from dual C-bar or C-bar and I-bar combinations are further enhanced by incorporating metal in the recording gap (ie: metal-in-gap or MIG type read/write heads). To reduce the prospect of erroneous readings from the gap at the interface between the main body flux path and one of the metal layers, it is known to space the MIG head at the non-recording interfaces in offset relation from the media recording surface by a wedge of non-magnetic material.
Contemporary superconductor material are evolving as are SQUID types of extremely sensitive magnetic field detecting structures. One configuration for a SQUID employs two parallel Josephson junction devices.
Despite the more recent advances in superconductor material, none of the known prior art has effectively harnessed the phenomenon so as to realize the highly efficient and high density magnetic reading and writing as is obtained by the present invention.